1. Field of the Invention
This invention relates to direct current (DC) machines, particularly to a direct current (DC) motor, and more specifically to improvements in an armature thereof.
2. Description of the Prior Art
As a multipolar DC motor, there has heretofore been used one shown in FIG. 1 for example.
More specifically, this DC motor includes magnets 52 as being a plurality of field poles arranged annularly at positions substantially equidistant from one another on the inner periphery of a cylindrical yoke 51 and an armature 53 shown in FIG. 2. This armature 53 includes a core 55 coupled to a rotary shaft 54 and a plurality of coils 56 being coil-wound on this core 55. The respective coils 56 are coil-wound in the lap winding in slots 57 formed in plural number in the core 55. A commutator 58 is coupled to the rotary shaft 54 and a plurality of brushes 59 are brought into sliding contact with the commutator 58.
Then, the brushes 59 and the commutator 58 feed the power to the respective coils 56 of the armature 53, whereby the armature 53 rotates, cutting the fields of the magnets 52.
However, since, in the conventional DC motor of the type described, the armature is constructed such that coils are coil-wound in the lap winding wherein a coil is overlapped another one adjacent thereto and this overlapping is repeated, such disadvantages are presented that excessively thick coil windings occur, whereby the usage at coil ends of the respective coils, which are portions not acting electromagnetically, is increased, so that the weight is increased, the cost is also raised, and moreover, improvements in performance is substantially suppressed. Because of this, there are such drawbacks that demands cannot be met for rendering the armature, in its turn, the DC motor, light in weight, thin in shape, compact in size, low in cost and high in resource saving capability, and moreover, heat radiating property is low.
Furthermore, according to the conventional technique, two winding end lines are led out of each coil, whereby the number of outgoing lines to be wound on the commutator is increased, so that it becomes difficult to connect the outgoing lines to respective segments of the commutator. Consequently, there has been a problem that, in order to secure the required number of segments, it is necessary to form the commutator into a complicated shape such as a generally two-stepped column-shape to have a large diameter as shown in FIGS. 1 and 2.
Further, to eliminate electromagnetically unnecessary coil portions, it is considered that the pitch angle of each pole should be made small to shorten the winding pitch of coil. However, according to the conventional technique, it has been unable to solve such a problem as described above.
Furthermore, the coil may be formed into a divided construction according to the conventional lap winding method. However, four or more brushes are required, whereby such disadvantages are presented that the number of brushes is increased, the degree of freedom in the provision of the brushes is lowered, and moreover, the automatic winding operation becomes difficult due to the decrease of mechanical strength of the coil by the reduced diameter thereof and the resultant disconnections.
On the other hand, in contrast to the above-described lap winding method, the winding construction according to the wave winding method has been widely used. According to the wave winding method, the portion of the start of winding is equal in length to the portion of the end of winding unlike the case of the lap winding method, so that a well-balanced winding can be obtained as compared with the lap winding method.
However, according to the conventional wave winding method, although the number of brushes can be decreased, the number of segments is increased, whereby it becomes necessary to form the commutator into a complicated shape such as a two-stepped column-shape to secure a required number of segments similarly to the case of the lap winding method. Therefore, the conventional wave winding method is disadvantageous in that the commutator should be of a large diameter and complicated in shape.